While I used Z16 core for a while i did not experience such issue but while I used xfce in Z16 core I experienced the same so I think it is xfce related issue
From settings, open Window-manager-Tweaks
On Accessibility tab, check ON for Automatically tile windows whem moving toward the screen edge.
Check OFF for Hide frame of windows when maximized.
Move to the Placement tab
"By default, place windows:"
Check ON for At the center of the screen.
Size your windows Correctly as you Want them to be, then close each out. Repeat this a couple times and the Window Manager should remember their placement and positions even after min or max is used.
In which case, please continue with Resizing them as you prefer them to be, then closing them normally. Repeat this a few times, then test if the windows resize incorrectly on Min / Max.